Most people land on this page in a mild panic, so here's the quick answer up front: the fastest way to tell if your computer has a virus is to look for a sudden change in behavior — new pop-ups, a browser that redirects itself, security software that's mysteriously switched off, or a machine that went from fine to crawling overnight. One symptom alone doesn't prove anything. Two or more showing up around the same time? Treat it as infected until proven otherwise.
We've been removing viruses and malware at our Somerville shop since 2011, and infected machines cross our bench every single week. This guide covers the ten warning signs we actually see (not the theoretical ones), how to check your computer yourself, and what to do if something turns up.
None of these guarantees an infection on its own. But these are the symptoms that, again and again, turn out to be malware once the machine is on our bench.
Computers slow down gradually as they age. What they don't do is go from fine on Tuesday to unusable on Thursday. Sudden slowness — long boot times, programs hanging, the endless spinning cursor — is the single most common complaint we hear from people who turn out to have an infection. Malware runs in the background and eats the resources your real programs need. It's not the only possible cause (a failing hard drive can make a computer crawl in exactly the same way), which is why we diagnose before we treat.
The modern version isn't just annoying ads. It's a full-screen alarm claiming to be Microsoft or Apple, sometimes with a robotic voice, almost always with a phone number to call. Here's the rule: real virus warnings never include a phone number. Don't call it, don't click anything, and never let anyone remote into your computer because a pop-up told you to. If the screen is locked up, hold the power button until the machine shuts off. These fake alerts scare more New Jersey residents into losing money than most actual viruses do.
Your homepage changed on its own. Your default search engine is suddenly something you've never heard of. You search on Google but the results route through strange websites first. That's a browser hijacker — a category of malware we remove from Chrome, Edge, Firefox, and Safari constantly.
A lot of malware disables your defenses before it does anything else. If Windows Security or your antivirus is off and won't stay on after you re-enable it, something is actively fighting you. That's not a glitch — that's a fight you're losing.
If friends or coworkers ask about a weird link "you" sent them, your account or your machine is compromised. The malware is using your contact list to spread itself. Change your email password immediately — from a different device, not the infected one.
New icons on the desktop, browser extensions you've never seen, a "PC optimizer" that appeared out of nowhere. Unwanted software rarely travels alone — where there's one stowaway, there are usually more.
If the computer is sitting idle with nothing open and the fan sounds like a jet engine, something is working hard in the background. Sometimes it's a stuck update. Increasingly, it's a cryptominer — malware that quietly uses your processor to mine cryptocurrency for someone else, running your electric bill and cooking your hardware.
If your documents and photos suddenly have scrambled names or odd extensions, or a message appears demanding payment to unlock them, that's ransomware. Stop using the computer right now — don't restart it over and over, don't download "fix" tools, and don't pay. Disconnect it from the internet and get help. We cover this in depth in our ransomware guide, and if files were damaged, data recovery may still be possible.
Some infections protect themselves by blocking the exact tools you'd use to find them. If Ctrl+Shift+Esc does nothing, or antivirus websites refuse to load while everything else works fine, take it as a confession.
Password-reset emails you didn't request, logins from locations you don't recognize, or accounts that suddenly lock you out — some malware exists purely to steal credentials. Change critical passwords (email and banking first) from a clean device, and turn on two-factor authentication while you're at it.
Seeing some of these signs and want to check before deciding anything? Here's how to check your computer for a virus yourself — free, using tools already on your machine.
Yes, Macs get malware — mostly adware, browser hijackers, and fake alert pop-ups. Check System Settings → General → Device Management for configuration profiles you didn't create (a classic adware trick), review your browser extensions, open Activity Monitor and look for unfamiliar processes using heavy CPU, and scan your Applications folder for anything you didn't install.
One honest caveat from the bench: a clean scan doesn't prove a clean machine. Modern malware's entire job is hiding from the tools you'd use to find it. When a computer comes into our shop, we run multiple scanners plus manual checks — because a single quick scan saying "no threats found" misses things weekly. If your symptoms continue after a clean scan, trust the symptoms, not the scan.
A good chunk of the "I think I have a virus" computers we check turn out to be something else entirely: a failing hard drive, a completely full SSD, bad RAM, overheating, or fifty programs fighting to launch at startup. The symptoms overlap almost perfectly with malware — which is exactly why we diagnose first. Our $75 diagnostic finds the real cause and is credited toward the repair either way. If it's a dying drive, virus removal wouldn't have fixed a thing — and you'd want to know before the drive takes your photos with it.
If the checks above turned something up — or the symptoms are stacking up — do these four things right now:
From there you have two routes. You can try removal yourself with a reputable scanner — our DIY vs. professional malware removal guide walks through where DIY works and where it tends to stop short. Or you can have it done professionally: our computer virus removal service in New Jersey is $149 flat rate — we deep-clean the system, verify it's actually clear, and have most machines back in 24–48 hours.
No pressure either way. If a free scan fixes it, genuinely great. The machines that end up on our bench are usually the ones where a scan "removed 14 threats" and the symptoms came right back two days later.
Speed of onset. Aging is gradual — a little slower every month. Infection is sudden — fine last week, miserable today. Sudden slowness plus any other sign on this list means check it. If you're not sure, a $75 diagnostic answers the question definitively and gets credited toward whatever fix is needed.
Yes — routinely. Antivirus catches known threats, but new variants appear daily, and plenty of malware is built specifically to evade or disable the popular scanners. That's why symptoms matter as much as scan results. For a deeper look at what the built-in protection does and doesn't catch, see our breakdown of whether Windows Defender is good enough.
Usually, but not always — and you lose your files and programs in the process. Some infections survive a standard reset, and a reset doesn't fix how the infection got in. We'd rather identify what's there and remove it while preserving your data, then close the door it came through.
Yes. Traditional self-replicating viruses are rare on Macs, but adware, browser hijackers, fake virus pop-ups, and malicious profiles are common — we clean them off MacBooks and iMacs every week. Don't assume a Mac is safe just because it's a Mac.
Some are built to do exactly that — keyloggers and info-stealers capture what you type and what's saved in your browser. This is why the first move on a suspected infection is to stop using that computer for banking and change critical passwords from a clean device.
If you're in Central New Jersey, skip the guesswork. Bring your computer to Dave's Computers at 75 N Bridge St, Somerville NJ 08876 (behind Bank of America) — no appointment needed, Mon–Fri 10am–5pm or Saturday 9am–2pm. We're a drop-off shop, and customers drive in from across Somerset, Middlesex, Hunterdon, and Mercer counties because the diagnosis is honest and the price is flat: $75 diagnostic credited toward your repair, virus and malware removal for $149, most machines back within 24–48 hours. Questions first? Contact us or call (908) 428-9558.